lit/TestRunner.py: [Win32] Check all opened_files[] released, rather than (obsoleted) written_files[].

In previous case,
RUN: foo -o %t
RUN: FileCheck < %t
RUN: bar -o %t

2nd read handle might prevent manipulation of 3rd %t in bar, to remove and rename.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@152916 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed